The present invention relates to an electrode for an electrochemical measurement apparatus, an electrochemical measurement apparatus using an electrode for an electrochemical measurement apparatus, an electrode for a biosensor, a biosensor using an electrode for a biosensor, a method of manufacturing an electrode for an electrochemical measurement apparatus, a method of manufacturing an electrode for a biosensor, a measurement method using an electrochemical measurement apparatus, and a measurement method using a biosensor.
Various devices for measuring the concentration of hydrogen peroxide in a solution are widely used to measure the concentration of hydrogen peroxide contained in a reducing agent used in a semiconductor fabrication process, to measure the concentration of hydrogen peroxide contained in a fungicide solution or an antiseptic solution used in a food manufacturing process, or to measure the concentration of hydrogen peroxide in water of a nuclear reactor.
Examples of a device for measuring the concentration of hydrogen peroxide in a solution include a device using an electrochemical reaction. Electrodes are immersed in a solution containing hydrogen peroxide. Carbon electrodes or electrodes of a noble metal such as platinum are used. Measurement is performed by detecting an electric current flowing when electric potential is applied.
This is because hydrogen peroxide is oxidized on a surface of the electrode to produce an oxidation current. Therefore, the concentration of hydrogen peroxide in the solution can be measured by measuring the oxidation current.
Meanwhile, measurement equipments in which a catalytic reaction of protein and an electrochemical reaction are combined with each other in addition to the aforementioned electrochemical reaction of hydrogen peroxide are widely used as a device for measuring the concentration of a substance contained in a variety of solutions.
Furthermore, there have been generalized a biosensor that converts a chemical substance in a solution into hydrogen peroxide by a catalytic function of an enzyme and measures the converted hydrogen peroxide with an oxidation-reduction reaction using the aforementioned electrodes. There have also been generalized an immunological sensor that allows a chemical substance (antigen) in a solution to react with an antibody and measures the concentration of the chemical substance in the solution by detecting an electric current produced by the reaction.
For example, if glucose is oxidized by glucose oxidase, gluconolactone and hydrogen peroxide are generated. The amount of hydrogen peroxide generated is in proportion to the concentration of the glucose.
Electrodes in which glucose oxidase has been immobilized on a surface of an electrode on which hydrogen peroxide is to be oxidized are prepared as electrodes used for a glucose biosensor. When those electrodes are immersed in a solution, the glucose oxidase oxidizes glucose, so that gluconolactone and hydrogen peroxide are generated.
Since the generated hydrogen peroxide is oxidized on the surface of the electrode, the concentration of the glucose in a sample can be measured by measuring an electric current produced by the oxidation.
Here, noble metals, which have higher oxidizability to hydrogen peroxide than other electrode materials, are used for the electrode for detecting hydrogen peroxide.
For example, Japanese laid-open patent publication No. 2001-116716 (Patent Document 1) and Japanese laid-open patent publication No. 2000-81409 (Patent Document 2) describe that platinum is preferably used as such an electrode material.
Meanwhile, platinum is expensive as an electrode material and has less workability as compared to other electrode materials. Therefore, electrode materials using substances other than platinum are used in some cases.
For example, Faming Tian and Guoyi Zhu, “Sol-gel derived iridium composite glucouse biosensor,” Sensors and Actuators B: Chemical, Elsevier B.V, (Netherlands), Volume 86, September 2002, pp. 266-270 (Non-Patent Document 1) discloses an electrode using iridium oxide.
Furthermore, Japanese patent No. 3854892 (Patent Document 3) discloses that iridium is one of preferable materials.
Those electrodes are used to measure the concentration of glucose by measuring an electric current after electric potential is applied to hydrogen peroxide.